linux-kernel - [PATCH] PCI: PM: Fix ordering of operations in pci_back_from

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Date:   Fri, 15 Oct 2021 18:45:59 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux PCI <linux-pci@...r.kernel.org>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: [PATCH] PCI: PM: Fix ordering of operations in pci_back_from_sleep()

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

The ordering of operations in pci_back_from_sleep() is incorrect,
because the device may be in D3cold when it runs and pci_enable_wake()
needs to access the device's configuration space which cannot be
done in D3cold.

Fix this by calling pci_set_power_state() to put the device into D0
before calling pci_enable_wake() for it.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/pci/pci.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/pci/pci.c
===================================================================
--- linux-pm.orig/drivers/pci/pci.c
+++ linux-pm/drivers/pci/pci.c
@@ -2638,8 +2638,13 @@ EXPORT_SYMBOL(pci_prepare_to_sleep);
  */
 int pci_back_from_sleep(struct pci_dev *dev)
 {
+	int ret = pci_set_power_state(dev, PCI_D0);
+
+	if (ret)
+		return ret;
+
 	pci_enable_wake(dev, PCI_D0, false);
-	return pci_set_power_state(dev, PCI_D0);
+	return 0;
 }
 EXPORT_SYMBOL(pci_back_from_sleep);